Greater and greater demands are made on an internal combustion engine, for example, of a motor vehicle with regard to a reduction of the fuel consumption and the produced exhaust gases while, at the same time, desiring an increased power. For this purpose, modern internal combustion engines are provided with a fuel supply system in which the feeding of fuel into the combustion chamber of the internal combustion engine is controlled and/or regulated electronically, in particular, using a computer-aided control unit. In this context, it is possible to inject the fuel into an air intake tube of the internal combustion engine or directly into the combustion chamber of the internal combustion engine.
In the last-mentioned type, the "gasoline direct injection", it is required to inject the fuel into the combustion chamber under pressure. For this purpose, provision is made for an accumulator into which the fuel is pumped by a pump and put under a high pressure. From there, the fuel is injected directly into the combustion chambers of the internal combustion engine via fuel injectors. In a homogeneous operation, the injection begins during the induction period of the respective cylinder, whereas in a fuel-saving shift operation, the injection is carried out during the compression stroke.
In both indicated methods of operation, the fuel quantity to be injected directly into the combustion chambers of the internal combustion engine via the fuel injectors, such as, possibly, also the start of injection or the end of injection are determined in advance by the control unit as a function of a plurality of performance quantities of the internal combustion engine. Subsequently, the fuel injectors are controlled by the control unit according to the determined values.
To start the internal combustion engine, special starting processes are provided. Particularly at low outside temperatures, the fuel quantity to be injected must be increased in the first injection in comparison with an internal combustion engine at operating temperature. This is necessary in order that, during the start, a sufficient quantity of low-boiling gasoline constituents are present for an ignitable air/fuel mixture. The increased fuel quantity during the start is also required to build up a wall film of fuel on the inside walls of the cylinders. During the following injections, the indicated increased fuel quantity to be injected is reduced to the normal fuel quantity to be injected for the internal combustion engine at operating temperature again.